The field of the disclosure relates generally to bearing assemblies, and more particularly, to journal bearing assemblies having flexibly mounted gas diffusing bearing pads.
At least some known turbomachines include rotor assemblies that include shafts, compressor impellers, turbines, couplings, sealing packs, and other elements required for optimal operation under given operating conditions. These rotor assemblies have a mass generating a constant static force due to gravity, and also generate a dynamic force due to imbalances in the rotor assembly during operation. Other static forces can be generated from geared turbomachinery. Such turbomachines include bearings to sustain and support these forces while permitting rotation of the rotor assembly.
At least some known turbomachines use oil lubricated bearings to support a rotor assembly while permitting rotation of the rotor assembly. Such oil lubricated bearings are particularly used in high performance turbomachinery, i.e., turbomachines capable of producing greater than 500 kilowatts (KW) of energy, where the mass of the rotor assembly and imbalance loading require significant vibration damping in addition to a significant static load carrying capacity of the bearing.
However, in certain turbomachinery applications, it is desirable to use non-oil lubricated bearings, such as sub-sea compression systems, highly corrosive working fluid environments, cryogenic environments, and high temperature applications. In such applications, at least some known turbomachines use magnetic bearing systems in lieu of an oil lubricated bearing. However, such magnetic bearing systems are relatively costly, require supplemental electronics systems for operation, and are highly complex in operation and setup.
As a result, at least some known rotary machines use gas bearings instead of magnetic bearings where a non-oil lubricated bearing is desired. However, the size of such rotary machines is limited by the ability of the gas bearings to support the weight of the rotor assemblies in such rotary machines and sustain dynamic loading of the rotary machines. The largest known commercially available rotary machines operating on gas bearings are microturbine generators with a power capability of 200 KW. Such microturbine generators include foil bearings, which generate a thin gas film between the bearing and the shaft of the rotor assembly through rotation of the rotor assembly. Such foil bearings, however, are limited in use to small-scale rotary machines because the hydrodynamic effects of using a thin gas film typically do not generate sufficient pressures to support heavier loads. Further, such foil bearings do not have sufficient damping capacity to accommodate rotor assemblies having larger masses used in higher power output machines.
Additionally, gas bearings are not easily adaptable for use in full-scale oil-free turbomachinery applications because of the damping capacity needed to sustain the dynamic loading experienced during operation of such full-scale turbomachinery. Rather, to meet the dynamic loading requirements of full-scale turbomachinery, at least some known rotary machines include squeeze-film dampers. At least some known squeeze-film dampers include a stationary journal and a cylindrical housing separated by a small gap of lubricant (typically oil) which generates dynamic pressures and film forces in response to rotor vibration. Such squeeze-film dampers typically require a lubricant flow circuit that includes a supply port and exit plenum, or in some cases, sealing assemblies to prevent the lubricant from leaking out of the bearing assembly. However, such squeeze-film dampers are prone to leakage despite the use of lubricant flow circuits and sealing assemblies. Further, such lubricant flow circuits typically require a complex bearing lubrication system for controlling lubricant delivery and scavenge. As a result, squeeze-film dampers having an open flow lubrication circuit cannot be practically integrated or used in combination with gas lubricated bearing systems.